NASHUA— A local dentist stabbed his wife to death and then hanged himself at the home they shared together for more than 15 years, according to investigators, who believe they have a motive in the case.

The couple, Reginald and Mary Danboise of 17 Middle Dunstable Road, was found dead Saturday morning by a visiting relative.

On Monday, the New Hampshire Attorney General’s Office said Dr. Reginald Danboise, 67, stabbed his wife, 63, twice in the chest before he hung himself in a detached workshop area at the rear of the pristinely manicured property.

His wife’s body was found in a second-floor bedroom, according to Jeffery Strelzin, senior assistant attorney general.

“He did kill her, and then he killed himself,” Strelzin said of the dentist.

According to the Office of the Chief Medical Examiner, Reginald Danboise’s death has been deemed suicide, and Mary Danboises’s death has been ruled homicide.

The circumstances leading up to the murder-suicide are still under investigation. Strelzin said a “sharp object” was used to stab Mary Danboise, but he would not elaborate on what type of weapon was used or whether it was discovered by authorities.

“We do have a clue as to the motive, at least we think we do,” Strelzin said, refusing to discuss the possible motive any further. He also would not comment on whether a suicide note or any other pertinent letter was discovered at the residence.

Friends and family of the Danboise couple are sharing their grief on various social media outlets.

“I hope that you are both together in heaven and whatever pain you both must have been in has disappeared,” Janice Caggiula of Nashua posted on Mary Danboise’s facebook page.

Another posting on the same site expresses words of support for the younger Danboise.

“I believe there is a world beyond this world where every soul finds peace, that there is a life beyond this life where love goes on and on,” wrote Jain Coveney of Weymouth, Mass. “God bless you Mary. You are so loved, and will be missed more than you could ever imagine.”

The couple worked together at Smiles of Nashua at 0 Profile Circle. Dr. Reginald Danboise was a dentist at the Nashua dental practice, along with A. Gerard Khan. Mary Danboise was an office administrator and dental assistant.

The dental office remained opened on Monday.

“At this time we don’t have any comment,” said a woman who answered the phone Monday afternoon.

Meanwhile, Nashua police will continue to interview neighbors, family and friends of the couple to learn all they can about the Danboises and determine exactly what precipitated the murder-suicide, according to Strelzin.

It could take a few weeks until more details in the case are released, he said.

Neighbors refused to comment on the police investigation on Monday.

According to the Smiles of Nashua website, Dr. Reginald Danboise has been active in the dental community for more than 30 years, and previously worked in a private practice in Boston for more than a decade before opening his office in Nashua.

Mary Danboise has also been involved in dentistry for about 25 years, working as a dental assistant and specializing in prosthetics, general and oral surgery.